... The Magnetic Sun . ... Galileo had guessed they were clouds floating in the Sun's atmosphere, obscuring some of its light. ... It turned out that the Sun has a polar field somewhat like the Earth's, but that it reverses its polarity during each 11-year cycle. ... Sunspot fields were evidently produced by electric currents, and it was well known that such currents could be generated by a " dynamo process ," by the motion of an electric conductor (e.g. the flow of solar plasma) through a magnetic...